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RE: HVFA Concrete

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Mark,

1) Cost can increase b/c formwork stripping can be (is) delayed due to
slower strength gain. This is especially a problem with walls and
floors.
2) We originally believed that finished would be a problem due to
anecdotal stories about "stickiness" and other issues from fly ash.
However, we have not had problems with finishing for walls or slabs.
3) Strength is a complete non-issue. Looking at some strength results I
just got today for a project using 50% fly ash (330 lb cement/330 lb fly
ash, normal weight):
	
	2 day 1700-1800 psi
	3 day 2500-2600 psi
	5 day 3600-3800 psi
	7 day 4200-4700 psi
	28 day 7500-8100 psi

We have obtained 56 day strengths as high as 11000 psi using 70% fly ash
(56 day) and lightweight concrete with 50% fly ash as high as 5600 psi
(28 day). 

I think a lot of the problem with fly ash is fear of the unknown (which
I think is a very good thing when it comes to structural engineering).
However, the unknown is becoming known and the "Green Building" aspects
of fly ash are real and significant. We are big advocates of its use and
fortunately we work with several forward-looking clients that are also
"Green Building" advocates. I think you will see rapidly expanded use in
the near future.

P.S. I love silica fume also but that is a different story. You can't
beat 15,000 psi concrete.

Eric Green
Walter P Moore


-----Original Message-----
From: Mark Webster [mailto:markdwebster(--nospam--at)hotmail.com] 
Sent: Friday, January 17, 2003 7:24 AM
To: seaint(--nospam--at)seaint.org
Subject: RE: HVFA Concrete

Eric,

Those are pretty healthy doses of flyash. What sort of adjustments do
you 
need to make to account for slower strength gain? Do slab finishers ever

have any trouble with finishing, or determining when to begin finishing?
Do 
you require the forms to stay up longer on wall and overhead work? Do
you 
specify a 56 day strength instead of 28 day?

The few ready mix companies I've spoken to around here are reluctant to
use 
anything over 30%.



Mark D. Webster, P.E.
Simpson Gumpertz & Heger, Inc.
41 Seyon Street
Waltham, MA
781-907-9000
mdwebster(--nospam--at)sgh.com
www.sgh.com





>From: "Eric Green" <EGreen(--nospam--at)walterpmoore.com>
>Reply-To: <seaint(--nospam--at)seaint.org>
>To: <seaint(--nospam--at)seaint.org>
>Subject: RE: HVFA Concrete
>Date: Thu, 16 Jan 2003 09:30:45 -0600
>
>Nels,
>
>
>
>We are regularly using 50%-70% fly ash on projects at this time in the
>Houston area, and the ready-mix suppliers are well versed in supplying
>the materials needed.
>
>
>
>Eric Green, PE
>
>Walter P Moore
>
>
>
>-----Original Message-----
>From: Nels Roselund, SE [mailto:njineer(--nospam--at)att.net]
>Sent: Wednesday, January 15, 2003 6:41 PM
>To: seaint(--nospam--at)seaint.org
>Subject: HVFA Concrete
>
>
>
>A number of articles in Concrete International over the past couple of
>years [for example, September 2002, July, 2002, March 2001] have been
>lauding the benefits of High Volume Fly Ash Concrete.  Durability, one
>of my particular interests because of my work on preservation of
>historic buildings, is high on the list of benefits.  For the growing
>number of those interested in Green Construction, the reduction in CO2
>emissions by 50% [at the rate of a ton of CO2 per ton of portland
>cement] or more to produce cement for a given amount of concrete is
very
>attractive.  55% to 65% cement replacement with Type F fly ash is
>proposed.  P.K. Mehta and V.M. Malhotra are prominent names in field of
>HVFA concrete.
>
>
>
>Are procedures for design and control of HVFA concrete mixtures
>available and being used in the construction industry?  Do you know of
a
>reference intended for design use [not a textbook]?  Is the Ready-mix
>industry geared up to produce HVFA concrete?
>
>
>
>Nels Roselund
>Structural Engineer
>South San Gabriel, CA
>njineer(--nospam--at)att.net
>


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